Although many advances in cancer therapy have been made during the last thirty years, many prevalent forms of human cancer currently resist chemotherapeutic intervention. For example, prostate cancer is the second leading cause of cancer death in men. The incidence of prostate cancer has increased 141.8% between 1973 and 1994. In 1998, new prostate cancer cases totaled 184,500, representing about one new case every three minutes, and 29% of all new cancer cases in American men. In 1998, an estimated 39,200 men died of prostate cancer. A life is lost to prostate cancer in this country every 13 minutes. According to the National Cancer Institute, the annual cost of prostate cancer to the country, including medical care, lost wages and lost productivity, may be as high as $15 billion.
Certain types of tumors are more amenable to therapy than others because they are more accessible to therapeutic agents. For example, soft tissue tumors such as lymphomas, and tumors of the blood and blood-forming organs such as leukemia, have generally been more responsive to chemotherapeutic therapy than have solid tumors such as carcinomas. One reason for the susceptibility of soft and blood-based tumors to chemotherapy is that they are physically more accessible to chemotherapeutic intervention. It is simply more difficult for most chemotherapeutic agents to reach all of the cells of a solid tumor mass than it is for such agents to reach the cells of soft tumors and blood-based tumors. While it is possible to increase dosages, chemotherapeutic agents are toxic at higher doses. Hence, conventional anti-tumor agents generally have a limited range of effectiveness against solid tumors and a need exists for the development of novel strategies for the treatment of solid tumors.
One strategy for treating solid tumors is to use anti-tumor cell antibodies to deliver a toxin to the tumor cells. However, this method suffers from certain drawbacks. For example, antigen-negative or antigen-deficient cells can survive to repopulate the tumor or lead to further metastasis. Also, a solid tumor is generally impermeable to large molecules like antibodies, especially when linked to a toxin molecule.
Recently, there is increasing interest in developing methods to induce site-selective thrombosis within blood vessels of a selected tissue and thereby infarct and destroy that tissue. This approach derived from the notion that in order for a tumor to grow beyond a critical size, it must recruit and activate endothelial cells to form its own new microvasculature (Denekamp 1990; Folkman 1992). Some investigators have therefore targeted tumor blood vessels for destruction in order to destroy the supply of oxygen and nutrients needed for local tumor cells to proliferate and survive (Huang, Molema et al. 1997).
WO 96/01653 discloses antibodies against tumor vasculature markers to deliver thrombogens to the vasculature of solid tumors. Vascular targeting strategies are also described in Burrows et al. (1992), in Burrows and Thorpe (1993) and in WO 93/17715. U.S. Pat. No. 6,156,321 discloses that a truncated form of Tissue Factor can bind to A20 lymphoma cells when co-administered with a bispecific non-neutralizing antibody that binds to Tissue Factor and to an antigen on the A20 lymphoma cells.